I'd like to build an email to fax gateway. The OS will be Linux. It will periodically check an email address via POP3 and derive the fax number, etc, from the email. The email will be encrypted to prevent "fax spam". I need to be able to specify the details via the CLI - so GUI software is a bad idea.

The question is, what is some good FOSS CLI fax software for Linux? Why do you recommend it?